<===> input.scss
@function test() {
  @return;
}

div {
  x: type-of(test());
}
<===> error
Error: Invalid CSS after "  @return": expected expression (e.g. 1px, bold), was ";"
        on line 2 of input.scss
  Use --trace for backtrace.

<===> error-dart-sass
Error: Expected expression.
  ,
2 |   @return;
  |          ^
  '
  input.scss 2:10  root stylesheet